ESTIMATION OF CARDIAC-OUTPUT BY NONINVASIVE ECHOCARDIOGRAPHIC TECHNIQUES IN THE CRITICALLY-ILL SUBJECT

We evaluated the accuracy of cardiac output estimations by three trans thoracic echocardiography techniques in critically ill subjects. This study was a prospective comparison study carried out in a general inte nsive care unit of a teaching hospital. The subjects had a broad range of diagnoses including pulmonary embolus, cardiogenic shock, septic s hock, Legionnaire's disease and perioperative myocardial infarction. A ll patients requiring pulmonary artery catheterization underwent echoc ardiographic cardiac assessment with comparison of findings to those o btained by thermodilution techniques. Nineteen studies on eighteen pat ients were performed, with cardiac output calculated by the two-chambe r Simpson's, four-chamber Simpson's, and left ventricular outflow trac t (LVOT) Doppler methods. Acceptable data was obtained in those patien ts without mitral regurgitation. There was good correlation between th e thermodilution technique and Simpson's two-chamber method (r = 0.91) , but less so with the Simpson's four-chamber method (r = 0.77). All s tudies were included in the LVOT Doppler method with a good correlatio n (r = 0.94). A plot of differences between methods using the Bland an d Altman statistical method indicated that only the LVOT Doppler metho d demonstrated acceptable agreement with a mean of 0.2 litres/minute, standard deviation of 0.82 litres/minute and 95% limits of agreement o f -1.5 to +1.9 litres/minute. We conclude that the LVOT Doppler method was the only one which demonstrated acceptable agreement between the thermodilution method and echocardiographic techniques in all critical ly ill patients studied.